Checkpoint. Best RX performance possible with current architecture

latest/Firmware/Inc/Receiver.hpp

@@ -44,12 +44,12 @@ public:
 
   bool init();
   VHFChannel channel();
-  virtual void startReceiving(VHFChannel channel);
+  virtual void startReceiving(VHFChannel channel, bool reconfigGPIOs);
   virtual void onBitClock();
   virtual void timeSlotStarted(uint32_t slot);
   void switchToChannel(VHFChannel channel);
 protected:
-  void startListening(VHFChannel channel);
+  void startListening(VHFChannel channel, bool reconfigGPIOs);
   bool addBit(uint8_t bit);
   void resetBitScanner();
   uint8_t reportRSSI();

latest/Firmware/Inc/Transceiver.hpp

@@ -43,8 +43,8 @@ public:
   void timeSlotStarted(uint32_t slot);
   void assignTXPacket(TXPacket *p);
   TXPacket *assignedTXPacket();
-  void startReceiving(VHFChannel channel);
+  void startReceiving(VHFChannel channel, bool reconfigGPIOs);
-  void startListening(VHFChannel channel);
+  void startListening(VHFChannel channel, bool reconfigGPIOs);
   void transmitCW(VHFChannel channel);
   void processEvent(const Event &);
 

latest/Firmware/Src/RadioManager.cpp

@@ -82,10 +82,10 @@ void RadioManager::start()
   //DBG("Radio Manager starting\r\n");
   configureInterrupts();
   if ( mTransceiverIC )
-    mTransceiverIC->startReceiving(CH_87);
+    mTransceiverIC->startReceiving(CH_87, true);
 
   if ( mReceiverIC )
-    mReceiverIC->startReceiving(CH_88);
+    mReceiverIC->startReceiving(CH_88, true);
 
   GPS::instance().setDelegate(this);
   //DBG("Radio Manager started\r\n");

latest/Firmware/Src/Receiver.cpp

@@ -63,10 +63,10 @@ bool Receiver::init()
   return true;
 }
 
-void Receiver::startReceiving(VHFChannel channel)
+void Receiver::startReceiving(VHFChannel channel, bool reconfigGPIOs)
 {
   mChannel = channel;
-  startListening(mChannel);
+  startListening(mChannel, reconfigGPIOs);
   resetBitScanner();
 }
 
@@ -77,11 +77,15 @@ void Receiver::switchToChannel(VHFChannel channel)
 }
 
 // TODO: This is a really, really long operation - over 320us !!!
-void Receiver::startListening(VHFChannel channel)
+void Receiver::startListening(VHFChannel channel, bool reconfigGPIOs)
 {
-  //bsp_signal_high();
+  if ( reconfigGPIOs )
+    {
+      // This takes about 140us
       configureGPIOsForRX();
+    }
 
+  // This takes 180us
   mChannel = channel;
   RX_OPTIONS options;
   options.channel = AIS_CHANNELS[channel].ordinal;
@@ -91,8 +95,12 @@ void Receiver::startListening(VHFChannel channel)
   options.next_state2 = 0;
   options.next_state3 = 0;
 
+  /**
+   * This can take up to 220us, that's 3 bit clocks!!!
+   */
+  bsp_signal_high();
   sendCmd (START_RX, &options, sizeof options, NULL, 0);
-  //bsp_signal_low();
+  bsp_signal_low();
 }
 
 void Receiver::resetBitScanner()
@@ -107,6 +115,14 @@ void Receiver::resetBitScanner()
   mRXPacket->reset();
 }
 
+/*
+ * TODO: Under a worst case scenario, this interrupt service method
+ * can take up to 320us to complete (that's 4 clock bits!!!)
+ *
+ * Re-architecting will be necessary to resolve this, and it will almost certainly
+ * require ditching FreeRTOS in favor of "bare metal".
+ */
+
 void Receiver::onBitClock()
 {
   // Don't waste time processing bits when the transceiver is transmitting
@@ -140,7 +156,7 @@ void Receiver::timeSlotStarted(uint32_t slot)
   if ( mSwitchAtNextSlot )
     {
       mSwitchAtNextSlot = false;
-      startReceiving(mSwitchToChannel);
+      startReceiving(mSwitchToChannel, false);
     }
 }
 
@@ -178,7 +194,7 @@ void Receiver::processNRZIBit(uint8_t bit)
       if ( mRXPacket->size() >= MAX_AIS_RX_PACKET_SIZE )
         {
           // Start over
-          startReceiving(mChannel);
+          startReceiving(mChannel, false);
 
           return;
         }
@@ -186,7 +202,7 @@ void Receiver::processNRZIBit(uint8_t bit)
       if ( mOneBitCount >= 7 )
         {
           // Bad packet!
-          startReceiving(mChannel);
+          startReceiving(mChannel, false);
           return;
         }
 
@@ -200,7 +216,7 @@ void Receiver::processNRZIBit(uint8_t bit)
         {
           mBitState = BIT_STATE_PREAMBLE_SYNC;
           pushPacket();
-          startReceiving(mChannel);
+          startReceiving(mChannel, false);
         }
       else
         {

latest/Firmware/Src/Transceiver.cpp

@@ -90,7 +90,7 @@ void Transceiver::processEvent(const Event &e)
 
 void Transceiver::transmitCW(VHFChannel channel)
 {
-  startReceiving(channel);
+  startReceiving(channel, false);
   configureGPIOsForTX(TX_POWER_LEVEL);
   SET_PROPERTY_PARAMS p;
   p.Group = 0x20;
@@ -155,9 +155,9 @@ void Transceiver::configureGPIOsForTX(tx_power_level powerLevel)
   setTXPower(powerLevel);
 }
 
-void Transceiver::startListening(VHFChannel channel)
+void Transceiver::startListening(VHFChannel channel, bool reconfigGPIOs)
 {
-  Receiver::startListening(channel);
+  Receiver::startListening(channel, reconfigGPIOs);
 }
 
 void Transceiver::assignTXPacket(TXPacket *p)
@@ -231,7 +231,7 @@ void Transceiver::onBitClock()
       if ( mTXPacket->eof() )
         {
           mLastTXTime = mUTC;
-          startReceiving(mChannel);
+          startReceiving(mChannel, true);
           gRadioState = RADIO_RECEIVING;
           reportTXEvent();
           TXPacketPool::instance().deleteTXPacket(mTXPacket);
@@ -267,7 +267,7 @@ void Transceiver::timeSlotStarted(uint32_t slot)
 
   // Switch channel if we have a transmission scheduled and we're not on the right channel
   if ( gRadioState == RADIO_RECEIVING && mTXPacket && mTXPacket->channel() != mChannel )
-    startReceiving(mTXPacket->channel());
+    startReceiving(mTXPacket->channel(), false);
 }
 
 void Transceiver::startTransmitting()
@@ -306,9 +306,9 @@ void Transceiver::startTransmitting()
 #endif
 }
 
-void Transceiver::startReceiving(VHFChannel channel)
+void Transceiver::startReceiving(VHFChannel channel, bool reconfigGPIOs)
 {
-  Receiver::startReceiving(channel);
+  Receiver::startReceiving(channel, reconfigGPIOs);
 }
 
 void Transceiver::configureGPIOsForRX()

latest/Firmware/Src/bsp/bsp_6_1.cpp

@@ -477,7 +477,7 @@ uint32_t bsp_get_system_clock()
 uint8_t bsp_tx_spi_byte(uint8_t data)
 {
   uint8_t result = 0;
-  HAL_SPI_TransmitReceive(&hspi1, &data, &result, 1, 10);
+  HAL_SPI_TransmitReceive(&hspi1, &data, &result, 1, 2);
   return result;
 }